CVE-2026-81535

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A client also does not check a\u00a0forwarded-tcpip\u00a0open against the forwards it registered with a\u00a0tcpip-forward\u00a0request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "In wolfSSH through 1.5.0 built with&nbsp;<code>--enable-fwd</code>,&nbsp;<code>DoChannelOpen()</code>&nbsp;in&nbsp;<code>src/internal.c</code>&nbsp;gates only&nbsp;<code>direct-tcpip</code>&nbsp;channel opens with the forwarding policy callback.&nbsp;<code>forwarded-tcpip</code>&nbsp;opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a&nbsp;<code>forwarded-tcpip</code>&nbsp;open against the forwards it registered with a&nbsp;<code>tcpip-forward</code>&nbsp;request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.<br>"}]}], "references": [{"url": "https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8", "tags": ["patch"]}, {"url": "https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c", "name": "Fix commit e396a0a4 (match forwarded-tcpip opens to registered forwards, PR #1148)", "tags": ["patch"]}, {"url": "https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c", "name": "Fix commit 79a7f299 (match forwarded-tcpip on every client session, PR #1220)", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "MEDIUM", "baseScore": 6.3, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"}}], "credits": [{"lang": "en", "value": "zhangph (GitHub afldl)", "type": "finder"}], "source": {"discovery": "EXTERNAL"}, "x_generator": {"engine": "Vulnogram 1.0.5"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-10-07T18:37:10.078645Z", "id": "CVE-2026-81535", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-07T18:37:36.186Z"}}]}}

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A client also does not check a\u00a0forwarded-tcpip\u00a0open against the forwards it registered with a\u00a0tcpip-forward\u00a0request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.", "supportingMedia": [{"type": "text/html", "value": "In wolfSSH through 1.5.0 built with&nbsp;<code>--enable-fwd</code>,&nbsp;<code>DoChannelOpen()</code>&nbsp;in&nbsp;<code>src/internal.c</code>&nbsp;gates only&nbsp;<code>direct-tcpip</code>&nbsp;channel opens with the forwarding policy callback.&nbsp;<code>forwarded-tcpip</code>&nbsp;opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a&nbsp;<code>forwarded-tcpip</code>&nbsp;open against the forwards it registered with a&nbsp;<code>tcpip-forward</code>&nbsp;request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.<br>", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-862", "description": "CWE-862 Missing Authorization"}]}, {"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-863", "description": "CWE-863 Incorrect Authorization"}]}], "providerMetadata": {"orgId": "50d2cd11-d01a-48ed-9441-5bfce9d63b27", "shortName": "wolfSSL", "dateUpdated": "2026-10-07T02:39:27.830Z"}}}, "cveMetadata": {"cveId": "CVE-2026-81535", "state": "PUBLISHED", "dateUpdated": "2026-10-07T18:37:36.186Z", "dateReserved": "2026-08-26T23:09:37.634Z", "assignerOrgId": "50d2cd11-d01a-48ed-9441-5bfce9d63b27", "datePublished": "2026-10-07T02:39:27.830Z", "assignerShortName": "wolfSSL"}, "dataVersion": "5.2"}

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